Electronic generator for contact and analog and command information

ABSTRACT

A display system for an aircraft including an electronic generator circuit for generating waveform signals which provide a pointer-marker on a cathode-ray tube, one end of which is normally positioned relative to a fixedly positioned reference mark. Various modes of operation are provided. In the compass mode, selected means provide signals to laterally displace the one end of the marker with deviation of the aircraft heading from a selected heading. In the omni mode, means responsive to the omni signals displace one end of the marker relative to the fixed reference with deviation of the aircraft heading from a selected heading, and effect lateral displacement of a second end of the marker with deviation of the aircraft from a selected track. A &#39;&#39;&#39;&#39;to-from&#39;&#39;&#39;&#39; symbol generator circuit is operative with the marker generator circuit to provide &#39;&#39;&#39;&#39;to-from&#39;&#39;&#39;&#39; information on the display. Crab means provide signals which adjust the pointermarker on the cathode-ray tube display to the heading to be followed for crabbing purposes.

United States Patent Balding 1 Feb. 15, 1972 154] ELECTRONIC GENERATORFOR 3,281,844 10/ 1966 Sabin ..343/ 106 X CONTACT AND ANALOG AND3,307,191 2/1967 Crane ..13/172 T x COMMAND INFORMATION OTHERPUBLICATIONS "Single Scope Displays. by A. Schlang et 111., MilitaryAutomation, Sept-Oct. 1958. pp. 172-173, copy in 343/1 12.

Primary ExaminerMalcolm F. Hubler [5 7] ABSTRACT A display system for anaircraft including an electronic generator circuit for generatingwaveform signals which provide a pointer-marker on a cathode-ray tube,one end of which is normally positioned relative to a fixedly positionedreference mark. Various modes of operation are provided. In the compassmode, selected means provide signals to laterally displace the one endof the marker with deviation of the aircraft heading from a selectedheading. ln the omni mode, means responsive to the omni signals displaceone end of the marker relative to the fixed reference with deviation ofthe aircraft heading from a selected heading, and effect lateraldisplacement of a second end of the marker with deviation of theaircraft from a selected track. A to-from" symbol generator circuit isoperative with the marker generator circuit to provide to-frominformation on the display. Crab means provide signals which adjust thepointer-marker on the cathoderay tube display to the heading to befollowed for crabbing purposes.

18 Claims, 65 Drawing Figures [72] Inventor: George H. Balding, LosAltos, Calif.

[73] Assignee: Kaiser Aerospace & Electronics Corporation, Oakland,Calif.

[22] Filed: June 30, 1969 [21] Appl. No.: 841,684

Related U.S. Application Data [63] Continuation of Ser. No. 378,892,June 29, 1964,

' abandoned. a

[52] U.S. Cl. ..343/108 R, 73/178 T, 340/27, 343/5 EM, 343/17 [51]lnt.Cl ..G0ls l/l8 [58] Field of Search ..343/17, 108,108 R, 108 SI,343/106, 107, 7.9, 7 TA, 6 TV, 5 EM; 73/178, 178 T; 340/27 [56]References Cited UNITED STATES PATENTS 2,732,550 1/1956 Reedy ..343/108X 2,931,026 3/1960 Nelson ..340/331 X 2,932,024 4/ 1960 Sant Angelo...343/107 X 2,967,263 1/1961 Steinhauser... ..343/108 X 3,128,445 4/1964Hosford ..73/178 T X 3,165,745 1/1965 Pike et al. ..340/27 X 3,237,1932/1966 Curry, Jr. et al ..343/108 .&

MODE

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sum as or 11 DISPLAY PRESENTATION DURING OMNI OPERATING MODE FIGJAFIG47F3 FIG. 7C

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INVENTOR. GEORGE H. BALDING v BYfi ATTYS.

PAIENTED EHISIBIZ 3.643.258

sum as 0F 11 DISPLAY PRESENTATION DURING OMNI MODE OF OPERATION FIG. QA

AIRCRAFT ON CORRECT GROUND TRACK BUT INCORRECT HEADING AIRCRAFT ONCORRECT HEADING BUT INCORRECT GROUND TRACK AIRCRAFT ON INCORRECT HEADINGAND GROUND TRACK INVENTOR. GEORGE H. BA LDING ATTYS PATENTEDFEB 1 s 1912SHEET 10 0F 11 FIG. I4 FIG 6 DIRECTIONAL CONTROL r J GYRO. 460 XFMR 462DIFF. AMPSI MIXER RECT 12? TRANS 4 3 493 E. E 2 -4 478 464 L as -"4ssELECTRONIC 400 POTENTIOMETER as new 1 I A 47| 472 P A L 0mm 95mgDERIVATI N 42 CKT. 42

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FIGI'ID IN VENTOR GEORGE H. BALDING BY M/%l/F7 l z/h j mm ADA-J90 FIG.I8

ATTYS.

ELECTRONIC GENERATOR FOR CONTACT AND ANALOG AND COMMAND INFORMATION Thisis a continuation of application, Scr. No. 378,892, filed June 29, 1964,now abandoned.

The present invention relates to a visual display system, andspecifically to a display system including a novel electronic generatorfor generating signals to provide a single integrated display, on adisplay device of information relating to different conditions of amobile unit.

A novel display device known in the field as a vertical displayindicator has been recently developed for the purpose of integratingvarious sets of information into a single display. In one application,the unit is used to provide a single display in an aircraft to replaceor augment the information previously obtained from a number of flightinstruments mounted in different varied locations on a complexinstrument panel. The display which is presented by the novel unitcomprises a stylized picture of the real world that not only integratesthe information necessary to establish the aircrafts attitude about itsreduced. The reduction of such response time is, of course,

important to the safety of the pilot.

A novel vertical display indicator which is operative in such manner hasbeen set forth in the patent to George H. Balding, U.S. Pat. No.3,093,822, which issued June ll, 1963, and is assigned to the assigneeof the present invention.

ln a basic display provided in one embodiment, the presentationcomprises a ground texture and sky texture separated by a horizon line.The horizon line in straight and level flight extends laterally acrossthe center of the display, and the horizon line is banked on the displaywith changes of the aircraft about the roll axis of the aircraft, and ismoved upwardly or downwardly with changes in the pitch of the aircraft.The ground texture includes a set of symbols which emanate from thehorizon and move in the direction of the lower marginal edge of thedisplay to create the illusion of forward movement of the aircraft overthe ground. The ground texture symbols are also displaced laterally onthe display with changes in heading, and the symbols are changed inperspective with changes in pitch of the aircraft. In more sophisticateddisplays, the symbols change in size with altitude, and the rate ofsymbol movement is related to the aircraft speed. A display providingsome or all of these basic symbols is identified hereinafter as acontact analog presentation.

ln addition to the contact analog presentation, the generator circuitrydisclosed in the above identified patent is also operative to provide aset of command symbols superimposed on the basic contact analoginformation to assist the pilot in carrying out different commands invarious flight modes. One basic command symbol comprises a wedge-shapedflight path superimposed over the ground texture so as to permit a pilotto navigate his aircraft along a path in the same manner as one drives'an automobile along a road or highway. The wedgeshaped path may becomprised of a plurality of parallel horizontal lines, successive onesof which are of an increasing width to create the appearance of aroadway extending in perspective toward a distant point. In certainembodiments tarstrip lines which extend across the path may also beprovided. In a simplified version, the flight path may be defined by twomarginal edge lines arranged to intersect with each other at an apex toprovide an inverted V.

In use of the arrangement there disclosed, the pilot merely maneuversthe aircraft to follow the path. Such a display unit provides valuableassistance to the pilot in the navigation and maneuvering of theaircraft. The degree of assistance is, of course, dependent upon theextent of information which the system is capable of displaying, and themanner of display of the information. That is, most aircraftnavigational equipment which is now used in the field is of themechanical indicator type, and the pilots have been extensively trainedto respond to the indications provided by such equipment. Accordingly,

in effecting a transition from the multiinstrument presentations nowexistent in most aircraft cockpits to an integrated presentation whichmore closely represents the real world, it is important in the interestof safety to provide a system which effects the display of theinformation in the integrated presentation in a manner which isconsistent with the conventional presentations now familiar to thepilots.

It is an object of the present invention, therefore, to provide a noveldisplay system in which a flight path and/or a contact analog displaymay be selectively connected for use with the different types ofnavigational equipment which are presently installed in existingaircraft, and specifically which is operative to present suchinformation in an integrated display which more closely simulates a realworld condition, and which nevertheless is consistent with, and relatedto, the presentations now provided on the multiinstrument panel.

As an aid to understanding the invention, a brief description of moreconventional navigational devices now installed in private, commercialand military aircraft is set forth hereat. In the less complexinstallations, for example, the navigational equipment may comprise asimpler gyrocompass which provides the pilot with the magnetic headingof the aircraft. The gyro compass is normally mounted on the instrumentpanel below the aircraft windshield, and the compass dial rotates withchanging headings to continually provide the magnetic heading to thepilot through a small readout window. Since the unit is mounted on theinstrument panel of the aircraft, the pilot is frequently required todirect his attention away from the aircraft windshield and the outerworld to obtain the magnetic heading reading provided by the compass.

It is an object of the present invention to provide a novel integrateddisplay which is intended to assist the pilot in flying a predeterminedcourse directed by a flight path command symbol, and particularly toprovide a display in which such type path is controlled by the gyrocompass of the aircraft. It is a specific object of the invention toprovide means for selecting a desired course of flight, signalderivation means which are operative to derive signals from conventionalgyro compasses of the type installed in many aircraft in the field todaywhich indicate deviation from a selected flight course, and generatormeans controlled by the signal derivation means to generate signalswhich provide a flight path on the display which indicate the headingselected, and also any variation of the aircraft to the left or theright of the selected heading.

It is yet another object of the invention to provide a system whichpresents an integrated display including such flight path with a horizonline which is continually adjusted to represent changes of pitch androll. in a preferred embodiment the system provides such display alongwith ground texture symbols which move to provide an indication ofrelative movement of the aircraft in the real world.

Another form of navigational equipment which is commercially availableand now installed in many planes in the field is known as omni/localizerequipment which, when adjusted in the omni mode, provides a reading ofthe magnetic heading which is to be flown to reach a selected station.Such unit includes a selector switch for selecting a desired station,and a dial which the pilot adjusts until a rotatable needle pointermoves to a vertical position. At such time, the pilot reads the magneticheading on a panel adjacent an indicator on the dial, which is theground track to the selected station. Such unit also has a to" and frommechanical indicator on the face thereof which indicates whether theindicated ground track is the course to or from" the station.

Obviously, with wind drift and the like, the use of such equipmentrequires frequent reference by the pilot to the aircraft instrumentpanel for the purpose of observing possible changes in the ground trackto the station, as well as reference to the gyro compass to ascertainthe heading of the aircraft relative to the indicated course. It is afurther object of the invention, therefore, to provide novel electroniccircuit means which are operative to derive a signal output from thecmni/localizer system when operated in the omni mode which controls thegeneration and display of the flight path, the near end of the pathbeing continually adjusted by such signals to indicate the ground trackwhich must be followed to reach the station selected by the omni system(i.e., the information now provided by the vertical pointer). In apreferred embodiment referred to herein as a ground stabilized path, thesystem also includes means for automatically adjusting the far end ofthe path to provide an indication of deviation of the aircraft headingfrom the selected heading to the station.

It is a further object of the invention to provide a novel coursedirector system which generates an aircraft stabilized path. That is, ifthe pilot registers a radial bearing to a desired station in the omnireceiver and the compass equipment, the novel course director systemprovides a flight path on the display which is automatically compensatedfor cross winds and the like, whereby guidance of the aircraft along theindicated path will bring the aircraft directly over the station. Statedin another manner, crabbing of. the plane to compensate for drift, crosswinds, etc., is automatically effected with maneuvering of the aircraftto follow the path provided on the display.

It is yet another object of the invention to provide signal derivationmeans for obtaining signals from such equipment when used in thelocalizer mode during landing of the aircraft at airports having ILSequipment, and means for coupling such signals to the flight pathgenerator means to provide a flight path display of assistance to thepilot during landing. In use of the localizer equipment now on aircraftduring a landing, the vertical pointer on the omni localizing equipmentindicates the location of the aircraft relative to the landing strip. Ifthe pilot should navigate to one side of the landing strip, the verticalpointer will pivot in a related manner to indicate the direction inwhich the aircraft must be maneuvered to return to its relative positionover the landing strip.

It is, of course, obvious that in landing under certain weatherconditions it may be desirable to utilize both the lLS equipment, andalso maintain visual observation with the real world. The difficultiesinvolved in maintaining contact with the real world through thewindshield and simultaneously visually observing the pointer on theinstrument panel are obvious. As a result, landing of an aircraft isfrequently a critical period and it is extremely desirable to providemaximum assistance in navigational aids to the pilot at such time.

It is a further object of the present invention, therefore, to provide adisplay which may be more readily observed, and which will more quicklyprovide the information required for the pilot to maintain the aircraftposition relative to the landing strip. It is a more specific object toprovide novel electronic means for deriving signals which vary with thetrack signals obtained from the localizer equipment, and means forcontrolling the near end of the path in accordance with the deviation ofthe aircraft heading from the heading of the localizer.

It is yet another object of the invention to provide novel means forproviding a display which includes such information as derived from thelocalizer equipment, in combination with means for controlling thesystem to simultaneously provide information relating to pitch, roll andyaw attitudes of the aircraft, whereby a complete integrated display ofreal world conditions is provided for the pilot in a single picture. Ina preferred embodiment, the display also includes ground textureelements which emanate from the horizon, and move toward the lowermarginal edge of the display to provide indications of aircraftmovement.

It is yet another object of the invention to provide novel signalderivation means for obtaining signals from the glide slope receiver onan aircraft, which in known devices is represented on a localizerreadout dial by a horizontal pointer which is displaced upwardly anddownwardly to indicate variation of the aircraft above and below theglide slope path. It is a specific object of the invention to providesignal derivation means which vary the width of the flight path on adisplay with deviation of the aircraft fro the from the glide slope.

In yet another embodiment, such deviations from the glide slope areindicated by movement of the apex (or far end of the path) upwardly anddownwardly relative to the horizon line.

Another well-known navigational aid device which is presently installedon a number of aircraft is commercially available as Automatic DirectionFinder Equipment (ADF). In the use of such equipment the pilot tunes hisADF receiver to a desired station, and a mechanical readout deviceincluding a pointer automatically provides the pilot with the bearing ofsuch station relative to the heading of the aircraft. To reach suchstation, the pilot need merely turn his aircraft from its headingthrough a corresponding number of degrees in the direction indicated bythe pointer.

It is a further object of the invention to provide novel signalderivation means for obtaining a signal from the automatic directionfinder system for use in controlling a flight path on a display device,and specifically for the purpose of controlling the flight path toindicate the heading which the pilot must fly to reach the desiredstation. It is a specific object of the invention to provide sucharrangement in combination with a contact analog display including atleast a horizon which is adjustable to indicate variation in pitch androll.

There is yet another form of navigational equipment which is installedin certain types of airplanes, and commercially available in the fieldas a Frequency Modulator Receiver Unit which operates with associatedground communication equipment to provide indications of thelocations ofvarious stations on the ground. Associated means in the aircraft may beselectively operated to locate the relative position of a desiredstation, and a readout device via pointer means indicates a steer right,steer left" requirement for the pilot to reach a desired station.

It is yet another object of the invention to provide novel signalderivation means for providing signals to control the flight path on adisplay device in such manner as to indicate to the pilot the necessarydirection of flight to reach the desired station. It is a specificobject of the invention to provide such arrangement, in combination,with a contact analog display including at least a horizon which isadjustable to indicate variation in pitch and roll.

The foregoing objects and features of the invention and others which arebelieved to be new and novel in the art are set forth in the followingspecification, claims and drawings in which:

F IG. l is a pictorial showing of a display which may be presented bythe display unit in one basic embodiment, including a mode selectorswitch which is used in selecting different modes of operation, andindicator means for identifying the mode selected at any time;

FIG. 2 is a block diagram of the novel control circuitry of the displaydevice selected by the mode switch in its different position;

FIG. 2A sets forth the positions of the mode switch in more detail; 1

FIG. 3 and 4 set forth pictorial representations of representativedisplays provided with operation of the device in the compass mode;

FIG. 5 comprises a block diagram of the circuitry used in control of theflight path generator with operation of the system in the compass mode;

FIG. 6 illustrates the novel circuitry for effecting control of theflight path generation in accordance with the information received fromthe aircraft gyro compass including the path far end control circuitry;

FIGS. 6A-6P set forth waveforms provided by the circuitry of F IG. 6,and the general path outline provided on the display in responsethereto;

FIGS. 7A-7D are pictorial illustrations of the display informationprovided during operation of the system in the omni mode;

FIGS. 8A-8C are further pictorial illustrations of the displaypresentations during the omni mode of operation; and associated FIGS.8D-8F illustrate the relative position of the aircraft and the omnistation with the presentations provided in FIGS. 8A- 8C;

FIGS. 9A-9C illustrate the display presentations which may be effectedduring the operation of the device in the instrument landing system(ILS) mode;

FIG. 10 sets forth the circuitry for providing path near end control;

FIGS. 10A-10I illustrate representative waveform outputs of thecircuitry of FIGS. 10 and the resultant flight path dis- P y;

FIG. 11 sets forth circuitry for providing the display of the symbol forto, from indications in the omni, ADF modes;

FIG. 11A is a pictorial showing of the to-from" symbol dis- P y.

FIG. 11B is an illustration of waveform signals which appear at theoutput of the symbol generator;

FIG. 12 sets forth the novel circuitry for controlling the flight pathin accordance ,with signals received from the ILS localizer equipment;

FIG. 13 illustrates the circuitry used with the ADF equipment of anaircraft to control the generation of the flight path display in suchmode;

FIG. 13A sets forth a voltage chart indicating voltages which occur inthe control system of FIG. 13;

FIG. 14 is a block diagram of the novel course director system;

FIG. 15 is a circuit schematic of portions of the course director systemof FIG. 14;

FIG. 16 sets forth an exemplary path which may be provided by the systemin its control of an aircraft;

FIGS. 17, 17A17Il set forth exemplary displays of aircraft positionsrelative to a bearing to a station and the displays provided in suchpositions; and

FIG. 18 sets forth a display including an indicator which locates theposition of the station relative to the director path.

GENERAL DESCRIPTION With initial reference to FIG. 1, there is shownthereat the display of a set of basic symbols which are provided by avertical display indicator 8 to assist the pilot in controlling theaircraft under both contact and instrument flight conditions. As thereshown, the display includes a ground texture 10 on a ground plane 11, asky plane 12 separated from the ground plane 11 by a horizon line 14,and a flight path 16 superimposed on the ground plane 11 to providecourse and/or heading information in accordance with the mode ofoperation selected.

The vertical display indicator 8, as shown in FIG. 2, comprises a flightpath generator 18, a contact analog display generator 18' and atelevision monitor 20. A gyro horizon 48 provides signals to control thevertical position of the horizon line 14 on the display, and roll sensor49 provides signals for rotating the yoke on the horizon 20 withvariation of the aircraft about its roll axis. The specific circuitry ofsuch system is set forth in detail in the above identified patent.

The present embodiment additionally includes a mode switch 22 which isoperable to different positions to connect control signals to the flightpath generator 18 from a plurality of novel circuits of the invention asset forth in detail hereinafter.

The television monitor 20 has a 30 cycle per second frame rate (60fields per second) and a 525 lone picture with a 2:1 interlace. In asimplified embodiment the timer means may be eliminated and the monitormay be energized by a frequency generator operating at approximately 12KC. The power input for the vertical display indicator (VDI) unit 8 maycomprise a conventional aircraft power source of twelve or 28 voltsdirect current. One complete VDI unit 8 including a contact analogdisplay generator 18', a flight path generator 18 and a display monitor20 in a miniaturized version was housed in a single unit SAXSAXIZ inchesand weighed approximately twelve pounds. The power consumption for theentire VDl unit was in the order of 40 watts.

The front panel display monitor 20 (FIG. 1) in the present inventionlocates a mode selection switch 22 which, as shown in FIG. 2A, isoperable to a plurality of positions including off, CA on, compass,omni, ILS, ADF and FM. The front panel of monitor 20 (FIG. 1) alsolocates a compass engaging switch 24 for use with mode switch 22 in thecompass mode, a brightness control knob 26 for controlling thebrightness of the display, a compass mode indicating lamp 28, an omnimode indicating lamp 30, an ILS mode indicating lamp 32, an ADF modeindicating lamp 34, and an FM mode indicating lamp 36. Lamps 28, 30, 32,34, 36 are illuminated whenever mode switch 22 is operated to thecorresponding position to select the indicated equipment for use incontrolling the flight path generator in the provision of the flightpath on the display unit. A fixed reticle 19 is located on the face ofthe display, as shown in FIG. 1, to provide a reference mark for thepilot. A pitch trim knob 38 permits adjustment of the horizon line 14vertically on the display so that the horizon line 14 may be adjustedinto correspondence with reticle 19 when the aircraft is in levelflight.

Mode switch 22, which may comprise a multilevel switch which closes aplurality of circuit completing contacts in each of its positions, isschematically shown in FIG. 2. Only certain of the contacts, such as60-65, 65, 72 and MS4-MS8 which are important to the disclosure of theinvention, are shown in FIG. 2. It will be apparent from the followingdescription that contacts, such as 62, may in fact be a series ofdifferent contacts at the different positions of the mode switch whichare tied together to complete the illustrated circuit to terminal Awhenever one of the positions noted adjacent the contacts 62 is selectedby the mode switch.

Briefly, as shown in FIGS. 2 and 2A as the mode switch 22 is operatedfrom the off position to the on" position an energizing circuit iscompleted from a 28 volt, 400 power source over contacts 60 and switch76 to the contact analog display generator 18' which, as thus energized,generates signals which provide the contact analog display on monitor 20(FIG. 1) including the ground texture 10, ground plane 11, horizon line14 and sky texture 12. A gyro horizon 48 is simultaneously connected toprovide pitch indicator signals to the contact analog 18', whereby thehorizon line display is varied in accordance with change of aircraftpitch. Roll sensor 49 is connected to control the yoke on the televisionmonitor 20, whereby changes of the aircraft about its roll axis resultin the corresponding banking of the horizon line 14 and associateddisplay on monitor 20.

Mode switch 22 at its contacts 60 maintains connection of the energizingcircuit to the contact analog display generator 18' in each of thesubsequent positions of mode switch 22, whereby the contact analoginformation is normally displayed in combination with the flight path.In the event that the contact analog display is not desired, switch 76(FIGS. 1 and 2) is operated to the open or off position.

With operation of the mode switch 22 to CA "on" position, power isconnected to contacts 60 on the mode switch 22, which contacts areclosed in the CA on position of mode switch 22, and are closed in eachof the subsequent positions of the mode switch 22 which are nowdescribed. Closure of contacts 61 when the mode switch is moved to anyof the subsequent positions supplies power to the flight path generator18 to effect generation of the flight path display. A far end blankingcircuit 67 is operative to blank the far end of the path (see forexample FIG. 7A). As will be shown, with selection of the compass modeby operation of switch 22 to the compass position and operation ofswitch CES 24, for example, the blanking circuit 67 is disabled and thepath far end appears. Absence of a path prevents the pilot from placingfalse reliance on a path which is not controlled by sensor signals.

Mode switch 22 is operative to a compass mode position (COMP) and insuch position is effective at its contacts M84 to selectively extendsignals derived from gyrocompass 40 by a novel compass derivationcircuit 40 to path far end control circuit 41, and at its contacts 62 isoperative to extend the far end path control signals to input circuit Afor the flight path generator circuit 18. As will be shown, with compassengage switch CES 24 closed, the control circuitry in such mode providesa flight path, the far end or apex of which is in registration withreticle 19 when the aircraft is on a selected course and which islaterally displaced from reticle 19 with changes in heading of theaircraft from the selected course.

Mode switch 22 is further operative to an omni position, and assumingthe pilot has selected the omni mode of operation of receiver 42 byoperation of omni receiver selector switch 43 to the omni position, modeswitch 22 closes contacts MSS to extend signals from omni receiver 42 tosignal derivation circuit 42 and path near end control circuit 47, andat its contacts 63 extends signals provided by path near end controlcircuit 47 to an input A on the flight path generator circuit 18.

As used herein, the path far end refers to the portion of the path whichis displayed at the path apex which, as shown in FIG. 1, occurs beneathreticle 19 for such condition of flight. The path near end is theportion of the path which occurs immediately adjacent the lower marginaledge of the display. The position of the path at the far end isdetermined only by path far end control circuit 41 and the position ofthe path at the near end is determined by the path near end controlcircuit 47. Accordingly, the apex of the path may be referred to as afirst informative marking, and the near end of the path may be referredto as a second informative marking. The location of the path betweensuch ends is determined by the signal output of both circuits 41 and 47.

Mode switch 22 in the omni position at its contacts 65 also connects theoutput of omni receiver 42 to the to-from circuit 66, and at itscontacts 67 connects the output of the to-from circuit 66 to the inputfor the television monitor 20. Additionally, with operation of the modeswitch 22 to the omni position, contacts M84 are closed to connect theoutput of the compass derivation circuit 40' to the path far end controlcircuit 41, and as will be shown, the far end of the path on the displaywill provide indications of variation of the aircraft from a selectedheading to a station and the near end will indicate indicationsvariations from the ground track to a selected omni station.

In the ILS position, the pilot operates switch 43 on the omni-localizerequipment 42 from the omni position to the ".8 position, and mode switch22 is operated to the lLS position. In such mode of operation, modeswitch 22 closes contacts M56 to complete a circuit from the ILS glideslope receiver circuit 45 to ILS glide slope signal circuit 45' and atits contacts 64 extends the signals derived from the ILS glide slopecircuit 45' to input circuit B on the flight path generator circuit 18.As will be shown, such control circuit effects adjustment of the pathwidth with deviation of the aircraft from the glide slope. Mode switch22 also closes contacts MSS to extend the signal output of the ILSequipment 45' (which indicate variations of the aircraft from the groundtrack of the glide path) to signal derivation circuit 42 and to the pathnear end control circuit 47; at its contacts 63 extends the outputthereof to input A on flight path generator 18 to control the near endof the path display to display deviations of the aircraft from theground track. Mode switch 22 in the ILS position also closes contactsM54 to connect the signal output of the compass derivation circuit 40',which, as will be shown, may be used to indicate deviation of theaircraft from the heading of the localizer equipment to the path far endcontrol circuit 41, the signal output of the control circuit 41 beingextended over closed contacts 62 to input A on the flight path generator18 to control the display of the far end of the path with variation ofthe aircraft heading from the heading of the localizer equipment.

Mode switch 22 further includes an ADF position in which contacts M87,M54, 62, 65, 67 are closed, contacts M87 being closed to couple signalsfrom the automatic direction finder receiver 44 to the ADF derivationcircuit 44 and contacts M84 being closed to couple the output signals ofcircuit 44' to the path far end circuit 41. The output signals of pathfar end circuit 41 are coupled over contacts 62 to input A on the flightpath generator circuit 18 to control the path far end in accordance withthe heading of a selected station relative to the aircraft heading. Inthe ADF position, contacts 65 are also closed to complete a circuit fromthe ADF derivation circuit 44' to the to-from circuit 66, and contacts67 are closed to connect the output of circuit 66 to the input formonitor 20 to effect the display of a symbol indicating the bearingextends to or from the selected station.

In an FM position, the mode switch 22 closes contacts M54, M88 and 62,the contacts M88 extending the signals from an FM receiver 46 to FMsignal derivation circuit 46, contacts M84 extending the output thereofto path far end circuit 41, and contacts 62 extending the output of thefar end control circuit to the input circuit A on the flight pathgenerator circuit 18.

The signal outputs of the flight path generator 18 and contact analoggenerator 18' and to-from circuit 66, as shown in FIG. 2, are connectedover path 74 to a video amplifier (not shown) and the beam modulationcircuit for the electron gun of the display tube in monitor 20. Points Aand B on the flight path generator are specifically identifiedhereinafter.

The specific manner in which the various equipments are selected by modeswitch 22 for operation in the control of the flight path displaygenerator 18 to display the desired information on the monitor 20, andthe specific manner in which the circuitry is operative to effect suchmanner of operation are now set forth in detail.

CONTACT ANALOG DISPLAY With operation of the mode switch 22 from the offto the CA on position, the power source is connected over contacts 60and switch 76 to the contact analog display generator 18' which operatesto provide the contact analog display of FIG. 1 on the monitor 20 in themanner set forth in U.S. Pat. No. 3,093,822. As indicated above, and asshown in FIG. 1, in the present embodiment the contact analogpresentation comprises a ground texture which is comprised of movingsymbols 10 which emanate from the horizon l4 and move across a groundplane 11, and a sky plane 12 which is divided from the ground plane 11by a horizon line 14 which is earth stabilized in pitch and roll.

The ground plane 11 upon which the ground texture 10 appears is darkgray at the horizon line 14, and gradually shades to a lighter gray nearthe bottom of the display area. The ground texture elements 10, shown inFIG. 1, are small at the horizon, closely spaced and slow moving, whileground texture elements at the bottom of the display are larger withgreater spacing, and move at a faster rate.

An aircraft reticle 19 is inscribed on the center of the faceplate forthe television monitor 20 so that the position of the horizon line 14 onthe display may be viewed with respect to the fixed aircraft reticle 19by the pilot, to thereby provide a quickly identifiable reference foruse in the determination of the roll and pitch attitude of the aircraft.Changes in the pitch angle of the aircraft are indicated by verticaldisplacement of the horizon line 14 with respect to the aircraft reticle19. Changes in roll attitude are indicated by banking of the horizonline.

Lateral motion of the ground texture elements indicates a change ofaircraft heading. The effect created is that of a quasirandom pattern ofelements or symbols forming a texture on the ground as viewed by a pilotthrough the windshield of his aircraft. All motion of the pattern on theground is seen as pilot motion; that is, rolling, pitching, yawing andforward motion are perceived as motion of the ground texture elementsdue to the motion of the aircraft relative to the ground.

The sky plane 12 which appears above the horizon line 14 is of a lightgray texture. As set forth in the above identified patent, other symbolsand cues may be provided on the basic contact analog display. Forexample, since the total vertical dimension of the display on monitor 20corresponds to a pilot viewing angle of 30, pitch lines may be providedwhich are ground stabilized in the same manner as the horizon line. whenthe aircraft is in a pitchdown maneuver greater than 15, the sky planedisappears from the top of the screen, and only the ground textureelements 10 and ground plane 11 are visible. A 30 pitch line appears atthe bottom of the screen and moves to the center of the screen as theaircraft pitches down through an angle of 30. In a similar manner if theaircraft is in a pitch-up maneuver greater than 15, ground plane I Idisappears from the bottom of the screen and only the sky plane 12 isvisible. The +30 pitch line appears at the top of the screen, and movesto the center of the screen as the aircraft pitchup" angle increases to+30". Pitch lines are also provided at 60 and 90.

Display generator 18 may also be operative to provide a roll pointercomprising a white mark fixed with respect to the raster which isoperative with a roll scale comprising a series of marks painted oretched on the face of the display and spaced at 10 intervals across thebottom of the screen to provide an indication of the aircraft rollattitude.

The contact analog presentation of FIG. 1 (without the flight path 16)is provided wherever the mode selection switch 22 is moved from the off"to the CA on position. With such operation, contact analog indicatorlamp 28 is also illuminated to indicate the energization of the displayunit in the contact analog mode. As will be shown, movement of the modeswitch to any of its other positions effects energization of additionalcircuitry, and also normally maintains the contact analog circuitryenergized so that additional information is provided on the displayalong with the contact analog information. Switch 76 is opened if thecontact analog information is not to be shown.

COMMAND DISPLAY In addition to the basic contact analog information theequipment is also operative to provide command symbols superimposed onthe basic contact analog information. One such symbol which hasparticular use with the contact analog is a flight path which may beprovided as a basic command symbol along, or in superposed relation withthe contact analog display. The flight path l6 as shown in FIG. 1 issuperimposed over the ground plane of the contact analog, and allows thepilot to navigate his aircraft in a manner similar to the manner inwhich one drives an automobile on a highway. The flight path as thereshown, comprises a wedge shaped symbol which creates the appearance of aroadway, the far end of which stretches to infinity, the roadway shapebeing defined by a series of parallel white lines, successive ones ofwhich are of an increasing width. As disclosed in the above identifiedpatent, a plurality of horizontal black tar strips may be provided atsuccessive positions in spaced relation with each other on the path.

Horizontal movement of the flight path apex relative to an aircraftreticle symbol 19 is used to provide different heading commandinformation. When the apex is superimposed on the aircraft reticlesymbol 19 (as shown in FIG. 1) the aircraft is on the correct commandheading. Additionally, the near end of the path may be displacedhorizontally as shown in FIG. 3, or the path apex may be laterallydisplaced as shown in FIG. 4. Lateral displacement of the near end ofthe path as shown in FIG. 3 with the path apex in registration with thereference reticle symbol 19 indicates that the aircraft is on thecorrect heading but is to the left of the track. Lateral displacement ofthe far end of the path to the right (as shown in FIG. 4) with the nearend in the normal central position would indicate that the aircraft ison track but is on the wrong heading. Other displays for differentheading and track conditions will be apparent therefrom.

As will be shown hereinafter, whenever certain information is notreceived for the path near and far end display, such section of the pathwill be blanked out to prevent the pilot from COMPASS INPUT WITH CONTACTANALOG MODE As indicated above, with the operation of the mode switch 22to the compass mode of operation, identified hereafter as the COMPposition, contacts 61 close to connect power to the flight pathgenerator 18, and thereby provide a display of the near end of theflight path in superimposed relation with the contact analog display;contacts M84 close to connect the aircraft gyro compass 40 and signalderivation circuit 40 to path far end control circuit 41, and contacts62 close to connect the output of control circuit 41 to control theflight path generator circuitry 18 in the provision of a flight pathdisplay which represents the information provided by compass 40 relativeto a selected course. With closure of compass engaging switch 24, thefar end blanking circuit 67' is disabled, and the far end of the pathwill appear on the display.

More specifically, in such method of use, the pilot first turns the modeswitch 22 to the COMP position, and as the near end of the flight pathappears, maneuvers the aircraft to the heading which is to be flown.Upon reading the selected heading (as shown by the compass) the pilotengages the compass engage switch 24 (FIGS. 1 and 2) and the far end ofthe flight path 16 will appear on the screen to provide a flight path inthe manner illustrated in FIG. 1. The far end of the path is now lockedto the selected comparison heading.

That is, any variation of the heading of the aircraft from the headingat the time of the operation of compass engaging switch 24 will resultin a corresponding displacement of the flight path 16 on the displayscreen. Stated in another manner, any change in the aircraft headingfrom the selected compass heading will result in a horizontaltranslation or displacement of the path apex to indicate the headingerror. The pilot in correcting for the heading error, flies towards thepath apex. Thus, if the path apex is displaced to the right of thereticle symbol (FIG. 4), the aircraft is turned to the right until thepath apex and the aircraft reticle symbol are once more coincident (FIG.1). Similarly if the path apex appears to the left of the aircraftsymbol, the aircraft must be turned to the left until coincidence of thepath apex and symbol l9 occur. The circuitry for effecting such mannerof operation is set forth in block form in FIGS. 2, 5 and in more detailin FIG. 6, and reference is now made thereto, for the purpose of morefully setting forth the manner of operation of the display device in thecompass mode.

With reference first to FIG. 2, with compress engaging switch 24 engagedthe mode switch 22 in the COMP position is effective at its switch armM84 to connect the signal output derived from gyro compass 40 byderivation circuit 40 to the path far end circuit 41, and mode switchcontacts 62 extend the output signals of circuit 41 to input circuit Afor the flight path generator circuit 18. As noted above, mode switch 22at contacts 60 also maintains the power connection to con tact analogdisplay generator 18' and at its contacts 61 connects power to flightpath generator 18.

As will be shown, in such manner of operation gyro compass 40continually provides compass derivation circuit 40' with signalsrepresentative of the deviation of heading of the aircraft from theheading which was selected at the instant of closure of the compassengage switch 24, and path far end control circuit 41 providesrepresentative signals over mode switch contacts 62 to input circuit Afor flight path generator circuit 18 to control same in the generationof a flight path which indicates the amount of deviation of the aircraftrelative to the selected heading. The specific manner in which suchdisplay is effected is now set forth.

PATH FAR END CIRCUIT 41 With reference to the block diagram of FIG. 5,the basic circuit arrangement for controlling the flight path generator18 in such mode is shown to comprise a gyro compass 40, compass engagingswitch 24 for energizing the lock-in equipment of the gyro compass 40, acompass signal derivation circuit 40, selection contacts M84 on modeswitch 22 which are operative in the COMP position to connect the outputof gyro compass 40 to the path far end circuit 41. Path far end circuit41 basically comprises a differential amplifier 81 including pathfar-end circuit adjustment means 83, push-pull emitter followers 85, andelectronic potentiometers 86, 87 which control the horizon sawtoothsignals received over input conductors 166, 186 from horizon linegenerator 69 and flight path generator circuit 18. With reference to theabove identified U.S. Pat. No. 3,093,822, the equipment of FIG. 5 willhave its conductors 166, 186 connected to a horizon line sawtoothgenerator (FIG. 2) which may be a conventional sawtooth generator of thetype 274 shown in FIG. of such patent which is connected to be energizedby horizon line pulses obtained over point C (resistor 416 in suchpatent).

With reference no w to FIG. 6, the specific detailsof the compassderivation circuit 40' and path far end control circuit 41 are set forththereat. Gyro compass 40 used with such circuit in one operativeembodiment comprised a commercial compass 976M-1 obtained from the LearCompany, which includes a compass engage switch 24 operative to connecta 12 volt DC signal to the gyro compass unit 40 as closed and a 12 voltdisabling signal to the far end blanking circuit 69. With operation ofswitch 24, associated means in the compass lock to the particular courseon which the aircraft is headed at the time of switch closure, andthereafter such means provide signals which indicate the variations ofthe aircraft from the selected heading. The gyro compass 40 is energizedby 28 volt, 400 cycle output of a conventional aircraft inverter whichis coupled over power conductors 78, 79 to the gyro compass 40.

With energization of gyro compass 40 by closure of the compass engagingswitch 24, an output voltage appears over conductor pairs 50, 51 and 52,51 which is in the order of approximately 2 volts. With variation of theaircraft in one direction from the course selected at the time of theclosure of the compass engaging switch 24, the voltage across conductors50, 51 will increase and the voltage across conductors 51, 52 willdecrease by a corresponding amount. If the aircraft deviates from theselected course in the opposite direction the amplitude of the voltageon conductors 52, 51 will be increased, and the amplitude of the voltageat the conductors 50, 51 will be decreased by a corresponding amount.Thus, with operation and closure of compass engage switch 24, the gyrocompass 40 will provide an indication of the amount and direction ofdeviation from the selected course.

1 The deviation representative output voltages are coupled over switchMSS to the path far end control circuit 41 over a filter networkincluding bridging capacitors 89, 91 which are connected betweenconductors 50, 51 and 51, 52 respectively for the purpose of minimizingtransient noise signals which might otherwise be introduced into thepath far end control circuit 41. A first voltage doubler clampingcircuit 102 comprising series capacitor 90 and diode 93, and a secondvoltage doubler clamping circuit 102 comprising capacitor 92 and diode94 are connected across the output conductors 50, 51 and 51, 52respectively for the purpose of providing output signals of doubleamplitude for use in the path far end control circuit 41, whereby theamount of amplification required in later stages of the circuitry isreduced.

The alternating current outputs of the voltage doubler circuits arerectified by rectifiers 104, 105 and coupled to a summing network 103comprising a first resistor 94' and a second resistor 96 connectedbetween conductors 50, 51 and 51, 52 to mix the two output voltagestogether, and provide a resultant positive or negative output signaldepending upon the value of the heading error (amplitude) and thedirection of the heading error (polarity).

A pair of capacitors 100, 101 are connected between the junction ofresistors 94, 96 in the summing network 103 and 1; ground. A pair ofcapacitors 106, 107 connected across the summing network 103 providefurther filter means for the input signals.

The output of the summing network 103 is coupled over conductor 108 andswitch arm MS4 (whenever the mode switch 22 is in the COMP position) tothe input for a differential amplifier 81 in the path far end controlcircuit 41 which comprises a pair of transistors 110, 118 which may beof the type commercially available as 2N9 10.

The collector of transistor 110 is connected over resistor 112 to a +20volt current DC source. The base is connected over conductor 109, switcharm MS4 to the output conductor 108 of summing network 103, and theemitter is connected over resistor 114 and an adjustable resistor 136 ina path farend adjustment circuit 83 to the collector of transistor 124.The collector of transistor 118' is connected over resistor 120 to +20volt source conductor, its base is connected to ground, and also overdiode 137 to 21 +10 volt source conductor, and its emitter is connectedover resistor 122 to the 'opposite'end of adjustable resistor 136.

The differential amplifier 81 is thus connected in a conventionalarrangement to minimize possible variations in amplifier gain as aresult of temperature variations. In the embodiment shown herein theamplifier 81 has a gain of approximately 3: 1.

Potentiometer 136 which is connected between the emitters of thetransistors 110, 118 in differential amplifier 81, has its adjustablearm connected to the collector of the constant current device 124 topermit adjustment of the amplifier signal output to different values. Aswill be shown, adjustment of the signal output effects a correspondingadjustment of the position of the far end of the path 16 relative to theaircraft reticle 19 (F IG. 1).

The constant current device is adjustment circuit 83 comprises aconventional transistor 124 which may be of the type available as a2N9l0 commercially, having a base connected to a voltage divider 126,128 which is connected between -20 volt DC and ground, and an emitterwhich is connected over resistor 130 to a 20 volt DC source. Inaccordance with established operating modes, the constant current device124 makes available a constant current for the transistors 110, 1 18 ofthe differential amplifier 81.

The output of the differential amplifier 81 is extended to the inputcircuits for push-pull emitter followers 85 which includes transistors140, 146 respectively connected in a pushpull arrangement. The baseelements of transistors 140, 146 in addition to being connected to theoutput circuit of differential amplifier 81 are connected over filtercapacitor 144 to ground. The collector of transistor is connected overdiode 142 to the +10 volt source and the collector of transistor 146 isconnected to ground.

The transistors 140, 146 operate as emitter followers to adjust theeffective resistance value to be provided by associated electronicpotentiometers 86, 87 for the sawtooth output circuits. It will beapparent that as the conductivity of one transistor of the pair 140, 146is increasing, the conductivity of the other transistor will bedecreasing, the nature of the conductivity and the output signals to theelectronic potentiometer 86, 87 provided by transistors 140, 146 beingdetermined by the polarity and amplitude of the signal of thedifferential amplifier 81 to the push-pull amplifier 85.

The emitter of the transistor 140 is connected to an electronicpotentiometer 87 which includes a photoresistor V2 having a lamp 180 andassociated photoresistor 182, a first pair of voltage limiter diodes172, 174 connected in parallel with the lamp 180 of the photoresistor V2and a pair of diodes 168, connected as short protection in the event offailure of the transistor 140.

The energizing circuit for lamp thus extends from +10 volts over diode142, transistor 140, resistor 176, lamp 180 and resistor 178 to ground.It will be apparent that the extent of energization of lamp 180 and thelight output thereof will be dependent upon the values of current flowprovided over transistor 140 which is in turn dependent upon theamplitude and polarity of the deviation signal provided overdifferential amplifier 85 by compass derivation circuit 40'.

The resistance element 182 of photoresistor V2 is connected in parallelwith resistor 1&4 between the in path sawtooth conductor 186 and out"path sawtooth conductor 168. Variation of the light output of lamp 180thus adjusts the value of the resistance provided by photoresistor V2 inthe sawtooth output path 168 as will be shown.

In one embodiment, with zero output from the compass derivation circuit40' (to indicate the aircraft is on the selected position) the signalapplied to the lamp 180 of photoresistor V2 was in the order of 5 volts.Such value was increased to volts and decreased to 0 volts in accordancewith the amplitude and polarity of the deviation indicating signalsprovided by compass derivation circuit 40.

The second electronic potentiometer 86 is similar to electronicpotentiometer 87 and comprises photoresistor V1, including lamp 160,photoresistor 162, voltage limiter diodes 152, 154, shunt protectiondiodes 148 and 150, and resistors 156, 158, connected in the manner ofthe elements of electronic potentiometer 87.

The second transistor 146 of the push-pull amplifier 85 is thusoperative in the manner of transistor 140 to control the flow of currentto the lamp 160 for photoresistor V1 over a path which extends from +10volts DC over resistor 158, lamp 160 in photoresistor V1, resistance 156and transistor 146 to ground. The degree of illumination of lamp 160 inphotoresistor V1, and therefore the value of resistance 162 provided byphotoresistor V1 in the sawtooth path extending from in conductor 166over resistor 164 to output conductor 168, will vary in accordance withthe extent of current flow over transistor 146 which is in turndependent upon the polarity and amplitude of the output signal providedover differential amplifier 81 by compass derivation circuit 40'. As inthe first potentiometer 87, a signal of approximately 5 volts is appliedto lamp 160 of photoresistor V1 when the aircraft is on the selectedheading, and the applied signal varies between 0-10 volts in accordancewith the direction and degree of derivation of the aircraft from theselected course.

As noted above, resistance members 162 and 182 of the photoresistors V1,V2 are connected respectively across resistors I64 and 184 in the pathsawtooth input circuits 166 and 186 which are connected to the horizonline sawtooth output conductors of generator 69. The input waveform overpath 166 comprises a negative-going sawtooth, and the input over path186 comprises a positive-going sawtooth. It will be apparent that thewaveform of the sawtooth provided over path 168 is determined by theeffective value of the resistors 162,

182 in the photoresistors V1, V2 respectively. In effect, therefore, thewaveform of the path sawtooth provided over conductor 168 is adjusted todifferent values by the adjustment of electronic potentiometers 86, 87which are in turn controlled by the amplitude and polarity of the outputsignals of the compass derivation circuit 40' which represents deviationof the aircraft from a selected heading. Illustrative examples of suchadjustment in the signal output, and the results thereof will now be setforth.

With reference to FIGS. 6A-6P, the first FIG. 6A illustrates thepositive-going sawtooth waveform input over conductor 186, and the FIG.6B illustrates the negative-going sawtooth waveform which is receivedover conductor 166, each of which sawtooths is received at the verticalrate of the raster. In the embodiment illustrated herein, the leadingedge of the sawtooths are locked or synced to the horizon line 14(FIG. 1) and accordingly the path apex willmove up and down with thehorizon line. It will be apparent moreover that in other embodimentssuch locking" of the path and horizon line may not be desired.

In the event that the aircraft is on the course selected by closing ofthe compass energizing switch 24, the signal output of the gyro compass40 at the output terminals 50, 52 will be equal, (+2 volts and -2volts), and the output of the summing network 103 will be zero. Withzero output signal coupled to differential amplifier 81, the outputsignal to the photoresistors V1, V2 by amplifier is in the nature of 5volts. Since the output of the photoresistor V1, V2 is equal andopposite and the sawtooths received over paths 166, 168 are of aninverse complementary order, zero output occurs over path 168 (FIG. 6C).Accordingly, with zero output to the flight path display generator 18,the novel display of the flight path 16 will be shown on the displaymonitor 20 (FIG. 6D).

Assuming now that the aircraft heading moves to the right of theselected heading, the path apex on the display monitor 20 will bedisplaced to the left to indicate that the aircraft should turn to theleft to return to the desired course (FIG. 6H). In the event of suchdeviation the output signal of the compass derivation circuit 40 will bemore negative to control transistor 146 to conduct more than transistor140. As a result, the light output of lamp increases, and the value ofresistance 162 decreases to cause the output circuit 168 to see more ofthe negative sawtooth coupled over path 166 (FIG.

In a similar manner, decreased conduction of the transistor 140 willcontrol the photoresistor V2 to increase the value of resistance 182,whereby the output circuit 168 will see less of the positive sawtooth onconductor 166 (FIG. 6E) and a waveform similar to that shown in FIG. 66is coupled over conductor 168 to the flight path circuitry 18 to effectthe output shown in FIG. 6H.

The manner of operation of the path far end control circuit 41 toprovide a more positive sawtooth output over circuit 168 with deviationof the aircraft heading to the left of the selected heading and therebythe display of FIG. 6L will be apparent from such description and thewaveforms 6I-6K.

In certain embodiments it may be desirable to provide a curved path onthe display in the manner shown in FIG. 6P, whenever the aircraft veersfrom the desired course. To obtain such display, it is merely requiredto place a capacitor in series with the sawtooth input path 166, 186,the capacitor being of a small enough value to differentiate thesawtooth and thereby provide a nonlinear sawtooth of the type shown inFIG. 6M, 6N, 60.

With disengagement of the compass engage switch 24, the far end of thepath disappears, and the path will no longer display the displacement ofthe aircraft from the selected heading. Movement of the mode switch 22to another position effects disconnection of compass derivation circuit40' from the path far end control circuit 41. Contacts 62 and 65 areopened if a position other than that noted adjacent such contacts isnext selected.

It is noted hereat that far end blanking circuit 67 basically includesan input circuit connected to the horizon line vertical sawtooth (of apositive-going signal), and electrical switch which is connected to theoutput of amplifier circuit (FIG. 19) of the above identified patent).With the compass engage switch 24 open, the circuit shorts the output ofamplifier 65 during the trace of the upper half of the path. Withclosure of the switch 24, the blanking circuit is disabled and the fullpath is drawn.

DISPLAY PRESENTATION DURING OMNI OPERATING MODE The mode switch 22(FIG. 1) as noted above is also operative to a further position OMNI" toclose contacts MSS to connect the signal output of an omni receiver 42(which may be Model 15F commercially available from the Aircraft RadioCorporation, Boonton, N.J.), to omni signal derivation circuit 42; andcontacts 63 to connect the output of path near end control circuit tothe input circuit A on the flight path generator circuitry 18. In suchposition of mode switch 22, the vertical display unit 8 provides apictorial display to the pilot of information which is now provided inthe above identified Model 15F by movement of a pair of needles on acourse indicator instrument (such as ARC IN-10) associated with theconventional omni equipment.

In the operation of such known type of device in the VCR mode, avertical pointer visually indicates the VOR or localizer informationreceived from associated converter circuits. The pointer is pivoted atthe top, and moves left or right to provide a visual indication of thelateral position of the aircraft with respect to the on-course signal ofthe VCR or localizer.

A To-From meter indicates whether the aircraft is going toward or awayfrom the station. A red flag is associated with each pointer, and theTo-From meter, to indicate the receipt or absence of output signals fromthe converter for such indications.

A course selector device on the omni indicator in the omni receiver 42identified above permits the selection of any course to" or from" a VCRstation, or indicates the magnetic hearing of the aircraft with relationto the VCR station. The course selector device includes a dial which islocated for movement relative to a graduated compass scale of 360. Atriangular-shaped pointer is used to indicate the course to a station,and a ball is used to indicate the reciprocal of the course on theindicator scale.

The to-from" meter is a zero-center, DC instrument which is used toprevent any ambiguity in reading of the course on the indicator dial.That is, the meter will show to" when the indicated bearing on thecourse indicator dial is a magnetic bearing to the station, and from"when the bearing on the course indicator dial is a magnetic bearing fromthe station. when reading the to-from meter it is necessary that thevertical pointer be in its approximate center position, whenever theaircraft passes through the neutral point of the localizer or thereceived signal is too weak to be reliable.

The omni equipment now installed in many aircraft may be used innumerous ways to provide navigational aids to the pilot. A few of thenavigational procedures which may be followed during the omni mode ofoperation include (a) determining the aircraft bearing relative to anomni station, (b) flying a desired course to" or from an omni station,(c) flying to an objective using two omni stations, (d) obtainingapproximate ground speed check by using two omni stations, (e)intersecting a localizer using an omni station, (f) approach procedure,and others.

An exemplary description of one manner of operation of the device inassisting a pilot in the omni mode to fly from a desired course to" orfrom an omni station is now briefly set forth hereat. The pilotinitially adjusts his omni equipment 42 to tune in the desired omnistation. The mode switch 22 is then turned to the OMNI position, and atcontacts 61 connect power to flight path generator 18 and at contacts 63close to provide signals which control the near end of the flight path16 to appear on the display, one example being shown in FIG. 7A. Thepilot then adjusts the course select knob on the omni receiver 42 sothat the near end of the path moves to the center of the display asshown in FIG. 7B. At this time, the pilot checks for the presence of ato-from symbol 190 on the display. If the symbol is in the positionshown in FIG. 7B, the aircraft is on a course directed toward thedesired omni station. If the symbol is in the position shown in FIG. 7D,the aircraft is on a course directed away from the selected omnistation.

The pilot then turns the aircraft until the compass heading on gyrocompass 40 is the same as the bearing shown on the course select dial ofomni equipment 42, and closes the compass engage switch 24. As a result,far end blanking circuit 67 is disabled and the far end of the path willappear on the display as shown in FIG. 7C.

The system is now ready for the pilot to use in the navigation of theaircraft to the selected omni station by simply following the directionsof the flight path 16. Heading error will be indicated by a horizontalshift in the path apex position from its registration with reticle 19(such error being provided, as noted above, by gyro compass 40, compassderivation circuit 40 and path far end control circuit 41 with variationof the aircraft heading from the compass heading selected) and groundtrack error will result in a horizontal shift in the path near endposition (the ground track information being obtained from the omnireceiver 42). Exemplary showings of such manner of presentation are nowset forth.

The flight path in the display of FIG. 1 isprovided whenever theaircraft is on the correct ground track and correct heading for aselected localizer station. That is, the path apex is in registrationwith the fixed reference reticle 19, and the near end of the path islocated centrally of the display.

With reference now to FIG. 8D a further flight condition is shownthereat. In such showing, the path 187 indicates the bearing of alocalizer station 188 as detected by the omni equipment on an aircraft189. As shown by the position of the aircraft relative to the path 187,the aircraft is on path 187, but the heading of the aircraft isincorrect. That is, if the pilot continued on the indicated course, theaircraft would quickly be moved away from the correct ground track. Itis readily apparent that a turn to the right will place the aircraft onthe correct heading as well as the correct ground track.

The flight path 16 which is provided on the display whenever the flightcondition of FIG. 8D occurs, i.e., the aircraft 189 is on the correctground track but on the incorrect heading is shown in FIG. 8A. As thereshown, the near end of the path is in its normal position centrally ofthe display, but the far end of the path has turned to the right fromthe fixed reference reticle 19. It will be readily apparent to the pilottherefrom that it will be necessary to turn the aircraft to the right tobring the aircraft to the heading indicated in FIG. 8A the aircraft willhave to turn from its present true heading of approximately 310 to atrue heading of 345. As the aircraft turns, the far end of the path 16will be moved back into registration with the reticle 19 as shown inFIG. 1 to indicate to the pilot that the aircraft is back on the correctheading.

In a further illustration set forth in FIG. 8E the aircraft 189 is shownto be on the correct heading, but on the incorrect ground track. Thatis, the aircraft 189 is displaced laterally to the left of the desiredpath 187. It is apparent therefrom that the pilot will have to turn theaircraft to the right to bring the aircraft to the proper ground track.Such flight condition is displayed in the manner shown in FIG. 88wherein the near end of the flight path is displaced to the right of itscenter position, to indicate to the pilot that the aircraft is to theleft of the correct ground track. In that the far end of the path 16 isin registration with the reticle 19, the aircraft is known to be on thecorrect heading.

In the disclosure of FIG. 8F, the aircraft is shown to be on theincorrect heading and ground track, and it will be apparent that thepilot must continue on his course to reach the correct ground track andthen turn left to the correct heading.

Such flight condition is represented on the display in the manner setforth in FIG. 8C. With reference thereto, it will be quickly determinedthat the near end of the path 16 is displaced to the right of its centerposition (i.e.; the aircraft 18Q is to the left of the correct groundtrack) and that the aircraft must continue to the right to reach thecorrect ground track.

Since the far end of the path 16 is displaced to the left of the reticle19, it will be apparent that upon reaching the track 187 it will benecessary to turn to the left until the end of the path is once more inregistration with reticle 19.

The small black square indicator symbol 190 in each of the FIGS. 8A, 8B,8C comprises a to indicator which indicates that the aircraft 189 isfollowing a path which is directed toward (rather than away from) anomni station, such as 188. The symbol 190 in the present equipmentappears as a solid black square approximately at inch inches in size,and when the displayed path is to an omni station the square is locatedin horizontal center of the flight path and near the apex or far end ofthe path (FIG. 8A-8C). If the symbol is located near the path base, theaircraft is heading from the station (see for example FIG. 7D).

Summarily, when the apex of the path 16 is superimposed on the aircraftvertical symbol 19, the aircraft, such as 187, is on the correctheading. If the near end of the path is in the center of the display,the aircraft is on the correct ground track. As will be shownhereinafter, the heading information

1. In a display system for a mobile unit, display means, a pathgenerator circuit for generating signals which provide a path on saiddisplay means including control means for varying the characteristics ofthe path displayed, a first signal circuit for providing informationsignals representative of deviations of heading of the unit relative toa predetermined selected heading including a signal generator circuitfor providing an output signal which varies in amplitude and polarity torepresent said deviation comprising a first and a second electronicpotentiometer circuit, each of which varies the resistance of a firstand a second circuit in accordance with the extent and direction of thedeviation, means for coupling a negative sawtooth to said firstpotentiometer circuit at a given rate, and means for coupling a positivesawtooth to said second potentiometer circuit at said given rate and inphase with said negative sawtooth, and summing means for providing asummated signal output of said first and second potentiometer circuits.2. In a display system for an aircraft including directional receivermeans on said aircraft, display means, a path generator circuit forgenerating signals which provide a path on said display means having anapex and a base end including control means for varying only theposition of the path apex on said display, a fixedly positionedreference mark located on said display means for said path apex, asignal derivation circuit for providing information signalsrepresentative of deviation of the heading of the aircraft from thebearing of a station selected by said directional receiver means, andmeans for coupling the output of said signal derivation circuit to saidcontrol means in said path generator circuit to correspondingly vary theposition of the path apex relative to saId reference mark withoutdisplacing the base end of said path.
 3. A system as set forth in claim2 which includes circuit means for generating a symbol display whichidentifies the bearing, at times, as the bearing to a station, and atother times as the bearing from a station.
 4. A system as set forth inclaim 2 which includes means for providing a further visual signal onsaid display means responsive to movement of said aircraft into apredetermined relative position with said station.
 5. A display systemas set forth in claim 2 which includes a further signal derivationcircuit for providing information signals representative of thedeviation of the aircraft relative to a selected track, and means forcoupling the output of said further signal derivation circuit to saidcontrol means to laterally adjust the position of the path base end onthe display to a correspondingly different position.
 6. In a displaysystem for a mobile unit having means including a directional receivermeans for selecting an associated station including means for providingsignals representing the ground track to said selected station andvariations from said track, display means comprising a cathode ray tubehaving a display area, marker generator means for generating waveformsignals which provide a pointer-marker having a first and second end onsaid display area including control means for modifying said waveformsignals to adjust the location of only one end of said marker on saiddisplay area without displacing the other end and for independentlyadjusting only said other end to provide an indication of the deviationfrom a selected heading, signal derivation means for providinginformation signals representative of the deviation of the mobile unitrelative to the track to the selected station indicated by said receivermeans, at least one immovable reference symbol fixedly positioned at apredetermined position on said display means for simultaneous viewingwith and referencing by said marker, means for coupling the output ofsaid signal derivation means to said control means in said markergenerator circuit to laterally vary the location of only one end of themarker on said display area relative to said fixed reference symbol toindicate the location of the mobile unit track relative to the selectedtrack to said station, and means for providing signals representative ofheading deviation to said control means to effect lateral adjustment ofonly said other end of said marker relative to said fixed referencesymbol to represent the heading deviation.
 7. A display system as setforth in claim 6 which includes symbol generator means for generatingfurther waveform signals to provide at least one additional symbol onsaid display means, and means for controlling movement of said symbol todifferent positions on the display area to indicate the track as towardor from the selected station.
 8. In a display system for an aircrafthaving localizer receiver means for selecting a localizer station,display means, a predetermined fixedly positioned reference symbol onsaid display, path generator means for generating waveform signals whichprovide a path on said display means with the apex of said path at saidreference symbol including control means for varying the shape of thewaveform to vary the position of the path base, the position of the pathapex and the path width, a first means controlled by said localizerreceiver means to provide signals representative of the position of theaircraft relative to a given track to a selected localizer station, asecond means including means on said aircraft for selecting the headingto said station, means for providing signals representative of theheading of the aircraft relative to said selected heading, a third meansfor providing signals representative of the position of the aircraftrelative to a glide slope provided by the selected localizer station,and means for coupling the output of said first, said second and saidthird meaNs to said control means in said path generator circuit toeffect the corresponding variation of the position of the path base, thepath apex and the path width.
 9. In a display system for a mobile unithaving display means, sensor means for providing signals relating to atleast one of the attitudes of the mobile unit, a path generator circuitfor generating signals which provide a path symbol on said display meansincluding control means for varying the path display with receipt ofdifferent signals from said sensor means, blanking means for blanking atleast a portion of said path symbol from said display, and circuit meansfor disabling said blanking means only during periods in which signalsare provided by said sensor means to said control means.
 10. In adisplay system for a mobile unit having electronic display meanscomprising a cathode ray tube having a display area, an electron beamand deflection means for said electron beam, a fixedly positionedreference symbol, path generator means for generating signals for saidcathode ray tube deflection means to provide a path on said display areahaving an apex including control means for applying signals to saiddeflection means to vary the position of the path on said display area,first means for providing signals representing deviation of the unitfrom a selected track, second means for providing signals representingdeviation of the heading of the unit from a selected heading, thirdmeans responsive to the output of said first and second meanscontinually providing the heading required to operate said mobile unitin a compensatory crabbing mode to the selected destination, and outputmeans for transmitting the output of said third means to said controlmeans for the path generator means to vary the lateral position of thepath apex on said display relative to said fixed reference symbol andthereby the heading to be followed to effect the proper crab attitude.11. A system as set forth in claim 10 in which said first meanscomprises a directional gyro for providing signals indicating the actualheading of the unit, a control transformer having a selector dial foruse in selecting the desired heading of the unit, and means forproviding output signals having an amplitude which varies as a functionof the difference between the heading selected and the actual heading ofthe unit.
 12. A system as set forth in claim 10 in which said thirdmeans comprises a differential amplifier stage having first and secondinputs and in which the output of said first means is connected to oneof said inputs, and the output of said second means is connected to thesecond one of said inputs, and means connected to the output of saiddifferential amplifier for providing signals of variable amplitude andpolarity to said output means.
 13. A system as set forth in claim 12 inwhich the last means includes means for providing sawtooth signals ofdifferent polarity and amplitude to said output means which representthe direction and amount of deviation of the heading selected and theactual heading of the unit.
 14. In a display system for a mobile unithaving compass means, display means comprising a cathode ray tube havinga display area, means for generating a horizon line, signal generatorcircuit means for generating waveform signals which electronicallygenerate a heading marker symbol on the display area of said cathode raytube display means for reference with a predetermined position on saidwaveform line when said unit is on a desired path including controlmeans for varying the display position of the one end of the markersymbol to different position along said horizon line, means forselecting a given compass heading, compass signal derivation circuitmeans for providing signals representative of deviations of the headingof the mobile unit from the selected heading, and means includingheading marker control means for coupling the signal output of saidcompass derivation means to said control means in said generAtorcircuit, said control means being operative to vary the location of saidone end of the marker symbol along said line relative to saidpredetermined position in accordance with the variance of the unitheading relative to said selected compass heading.
 15. (In lieu ofprevious claim 21) In a display system for providing directionalinformation relative to a selected station; cathode ray tube displaymeans including raster generator means, a first symbol generator meansfor providing signals which produce a first symbol on the raster whichpresents directional information on the display for said device, andto-from circuit means including input means connected to saiddirectional means over which a first signal is received whenever saidmobile unit is proceeding toward a selected location, and a secondsignal is received whenever said mobile unit is directed away from saidselected location, a second symbol generator means for generating asecond symbol on said display means including first means for generatinga first pulse set at the vertical rate of the raster, and second meansfor generating horizontal pulses at the horizontal rate of the raster,and means for generating symbol display signals only during thecoincident time period of said first and second pulses in a rastertrace, and symbol positioning means connected to said input meansresponsive to said first and second signals to enable said second symbolgenerator to position said second symbol at correspondingly differentpositions on said display means relative to a predetermined positionwhich represents the selected location.
 16. A system as set forth inclaim 15 in which said symbol positioning means is operative responsiveto said first and second signals from said input means to provideenabling signals which control the time of generation of said firstpulse by said first means at correspondingly different times in theraster trace, to thereby adjust the vertical position of the secondsymbol on said display.
 17. A system as set forth in claim 15 whichincludes signal derivation means connected to said first symbolgenerator means for providing signals to said second means to controlthe time of generation of said horizontal pulses in each line trace ofthe raster to thereby adjust the lateral position of the second symbolon said display means.
 18. (In lieu of previous claim 24) In a displaysystem for a mobile unit which has directional means for providingdirectional information relative to a selected location; cathode raytube display means including raster generator means, a first symbolgenerator means for providing signals which produce a first symbol onthe raster which presents directional information on the display forsaid device, to-from circuit means including input means connected tosaid directional means over which a first signal is received wheneversaid mobile unit is proceeding toward a selected location, and a secondsignal is received whenever said mobile unit is directed away from saidselected location, a second symbol generator means for generating asecond symbol on said display means, symbol positioning means connectedto said input means responsive to said first and second signals toenable said second symbol generator means to position said second symbolat correspondingly different positions on said display means relative toa predetermined position which represents the selected location, andblinker circuit means including detection means connected to said symbolpositioning means to detect movement of the mobile unit over theselected location, a timing circuit enabled responsive to detection ofsaid position by said detection means to provide a series of timingsignals, and means for coupling said timing signals to said symbolgenerator means to vary the size of the second symbol at a predeterminedrate to thereby provide the appearance of a blinking symbol while saidmobile unit is over the selected location.